The majority of rotary turbine ventilators are made of galvanized iron. Some rotary turbine ventilators are made of aluminum and plastics. In the manufacture of ventilators made of galvanized iron, the vanes of the rotary element are usually affixed to the base ring of the rotary element by spot welding or by riveting. Spot welding of aluminum is difficult and expensive. Because of the low resistance of aluminum to electric current, the welding current flow is high. The welding current can be reduced by reducing the pressure between the parts to be welded together, but this is difficult to control and even so the welding current is higher than with galvanized iron. Furthermore, the welded together aluminum parts must be held together to allow time for the welds to fuse, which slows production and is expensive. Riveting of aluminum parts together, particularly thin parts as are used in manufacture of rotary turbine ventilators, is not particularly practical because of the softness of aluminum.